Weak charged current induced electron and positron scattering off proton at JLab and MAMI energies

Abstract

The development of next-generation, high-luminosity, and high-precision charged lepton beam facilities at JLab and MAMI has opened, in recent years, a new frontier in the exploration of weak interaction processes induced by electrons and positrons in the neutral current sector, which can also be used to study weak interaction processes induced by charged currents. In particular, these processes in the intermediate energy regime, spanning from a few hundred MeV to a few GeV, play a crucial role in understanding electroweak dynamics, nucleon structure, and hadronic response functions. This review presents a comprehensive theoretical study of weak charged-current interactions of electrons and positrons with free protons, encompassing quasielastic scattering in both the strangeness conserving and strangeness changing channels, together with inelastic production of the $P_{33}$(1232), $P_{11}$(1440), $S_{11}$(1535) resonances, $η$ and $K$ mesons, and associated production of strange particles. We analyse differential and total cross sections, polarization observables of the final baryons, and spin asymmetries of the proton target, demonstrating their sensitivity to the underlying weak interaction dynamics and to possible second class currents, thereby enabling stringent tests of G- and T- invariance. The explored kinematic region also offers a unique and independent opportunity to constrain the axial vector sector of the weak interaction, and it provides a discussion of alternative ways to determine the axial dipole mass in the quasielastic scattering region, a fundamental parameter that is in debate for nearly two decades. It also focuses on the study of the axial-vector form factors associated with the excitation of the $P_{33}(1232)$ resonance in a manner that is free from the uncertainties inherent in their determination from studies of (anti)neutrino-induced weak processes.